URGENT: simulated hydraulic heads always too high

Hi everyone,

I have seen that this question has been already discussed, but I am also getting the same problem.
I am doing a mass transport for unsaturated and saturated zone. Before doing mass transport, I wanted to calibrate the flow. But every time my simulated hydraulic heads are higher than actual values.
My model is:  In unsaturated zone, I have 7 layers, while saturated zone have 3 layers. In layer 1 of saturated zone, I have 20 observation wells and also a river (1st kind BC). I am running this model for 60 years and have observed hydraulic head for two years.
When I started to calibrate the model, computed heads are too high (about 6 to 8 m). I tried to reduce the flux from boundaries, but it's not effecting a lot, then as a second step, I tried to increase the hydraulic conductivity for saturated zone, it is working but still I have a high error.
Now I am concern about the source of this error ? Do I need to play hydraulic conductivity of unsaturated zone also?

Or I need to change BCs for river ?

Hard to tell from the description, but in case the river in reality has a significant clogging layer (and is infiltrating), a switch to a Fluid-transfer BC for the river might be a good idea.

Thanks Peter,
Actually we don't have much information about the infiltration from river. Based on water level, we decided to use it as a 1st type boundary condition.
If it is possible to use different type of BCs in this scenario.